Production of medium-temperature coke



Patented July 6, 1937 COKE PnonUoTIoN or MEDIUM-TEMPERATURE tion ofDelaware No Drawing. Application January 19,1934, Se-

rial No. 707,419. in Germany January 20,

1 Claim.

My invention relates to the carbonization of fuel, such as finelydivided and well coking coal, especially bituminous coal and the like,and has particular reference to the so-called medium 5 temperaturecarbonization of fuels, that is, a carbonization process which iscarried through in such a manner that no portionof the coke produced,when gradually reheated in a closed space, for instance in a closedelectric furnace, begins to give oi gas outside the range of temperatureof from 609 to 756 centigrade.

The temperature at which gases begin to escape from coke being slowlyreheated in an air-tight oven is determined in the usual manner bytracing the tangent on that section of the curve of carbcnization, whichshows uniform formation of gases. By curve of carbonization I mean acurve which indicates the quantity of gas delivered at differenttemperatures by a determined quantity of coke when gradually heated. In

order to facilitate comprehension, it may be mentioned that the usualhigh temperature coke or blast furnace coke begins to give off gases attemperatures of from 780 to 830 centigrade or more. i

In the medium temperature carbonization the coal is heated preferably ina chamber coke oven made of a suitable ceramic material, such asfire-clay bricks, to a temperature of about 600- ?56" centigrade, thewalls of the coking chamber being kept at a temperature, measured on theinner side of the chamber walhwhich does not exceed the aforesaidtemperature. The coke is withdrawn from the coking chamber as soon asthe condensable hydrocarbons cease to escape from the coking charge. Inthe medium temperature carbonization an easily inflammable and reactivecoke in large solid pieces is obtained which burns without smoke and asto'its properties of 40 combustion closely resembles thenaturalanthracite or semi-anthracite. 'In addition, byproducts areobtained which practically have the same market value as the knownby-products of the high temperature carbonization. In this latterrespect the medium temperature carbonization process is superior to theknown low temperature carbonization which preferably is carried out,

in iron retorts or the like.

The object of my invention is to provide improvements in the mediumtemperature carbonization of fuels, especially finely divided wellcoking coal of all sorts, in such a manner, that the carbonizationprocess proper can be carried through within a shorter time and thusnotably more economically than it was hitherto possible.

In order to produce medium temperaturecoke in an economically stilladmissible relatively short coking time, the mass to be carbonized musthave the best possible heat conductivity and the consumption of heatrequired for the carbonization (ill. 202-20) must be as small aspossible. Furthermore, the

usualp-ushers. With most of. the well coking coal sorts boththeseconditions are improved to the desired extent by adding finelydivided coal which has been subjected to a preliminary heat treatment attemperatures below its softening point, or, finely divided coalparticles obtained by the dry heating of coal to temperatures slightly 1above the softening point (low temperature coke).

The above additions when compared with crude coal, possess acomparatively high heat conductivity. Consequently, mixtures of crudecoal and the above indicated additions require a notably shorter'cokingtime than pure crude coal. Besides, the contraction of the coal andthusof the product of the carbonization isimproved by the additionsindicated to ,such an extent, that practically no difficulties arise inpushing from the cokingohamber medium temperature coke obtained bycoking a mixture of crude coal and the above additions. f r I Hitheretothe mixture of crude coal and one of the above named additions has beensubjected to the medium temperaturecarbonizationin cold state. .With awidth of the coking chamber of about 350 mm. the carbonization timeamounts to about'24 hours. This time, however, is very long, consideringthe comparatively high costs of V the medium temperature carbonizationplants,

' that means, the output of the coking plant is very small with relationto the'invested funds, to obtain a satisfying lucrative coking process.

Now, according to my present invention, in

order to accelerate the coking process proper of the medium temperaturecarbonization process and thus to improve the economy of the process,the mixture of finely divlded, well-coking crude coal and an addition ofthe kind indicated above is previously to being filled into the cokingchamber, preheated and that to temperatures lying-bejlow that point atwhich the mixture softens or,"

cakes together, and thereupon is charged in such preheated state intothe coking chamber.

It has already been suggested to preheat to temperatures below thesoftening point, previous.

to the carbonization, a badly coking co'al'that is to be subjected tohigh temperature carbonization. These proposals, however, never havebeen realized successfully, as tests have shown that no heated, badlycokin'gcoal. is of a notably lower quality than coke made from crudecoal charged in cold and wet state. This results from the feature whichfrequently is overlooked, viz., that the badly coking coal sorts,whenpreheated even in anhermetically closed space, more or less lose theircoking capacity which already is small in itself. On, the other-hand,when finely disintegrated cold crude coal with a moisture of more thanabout 10% is used, the coal entersthe coking chamber in the state ofhighest baking 'capac ity and, owing to the comparatively highpercentage of moisture, it'is maintained at a low temperature for arather long time during the carbonization, so that also the preheatingperiod of the coal during the carbonization processis remarkablyshortened, and consequently, those alterations of the substance of thecoal cannot occur at all or to a verysmall extent only, whichunfavourably influence its coking capacity.

' In contrast thereto; I have discovered by my tests,'that well-cokingcoals, that is, coals rich in bright coal, which coke very well and havea high content of binding substances, can be preheated for aconsiderably longer period of time, without affecting the originalbaking capacity seriously. Suchwell coking coals, however, arepreferably used in the medium temperature carbonization,

as they possess the capacity of binding in a sufiicient quantity of theabove indicated additions, which are required for the economicalcarrying out of the medium temperature carbonization. 7

'I obtain very importantadvantages unknown hitherto by preheating thematerial to be charged ious influence being exerted on the quality ofthe produced coke by the preheating of the mixture to be coked.

Thus the economy of the medium temperature carbonization issubstantially improved by the process according to my invention.

A further advantageous efiect of my invention resides in the fact, thatit is now possible, under certain circumstances, to carry through themedium temperature carboni zation in the usual coking chambers ofa widthof more than 350 mm., without the carbonization time needing to beprolonged to such an extent, that the coke gives off gases to a largeextent in the marginal layers; that is, up to the extent to be observedin the high temperature carbonizati'on. ,Consequently; the applicationof my process also secures in cokingrchambers of greater width theproduction of a technically homogeneous medium temperature coke of goodquality. The somewhat longer'carbonization time can be tolerated in mostcases ofexisting coking plants withv wider coking chambers withoutdisadvantage, since these older plants as a rule already have beenredeemed'completely, so that the coke is not re- 7 V quired to carry theinterest on the invested capital.

a My improved coking processis carried through ,in practice for exampleinthe 'following'manner: 75

A mixture composed of crude coking coaland the addition, for examplesemi-coke, and containingabout from to well coking coal and further asmall percentage of small coke as it remains inthe disintegration of themedium temperature coke,'-is preheated, preferably in a hermeticallysealed container, to a temperature of the softening point of the coal orto that/point at which the mixture cakes together. The temperaturetowhich the mixture of coal and semicoke is to be preheated, dependsupon the properties of the coal to be treated. As preheating devices Iuse with advantage the usual rotary drum furnaces with direct or betterindirect heating appliance. From these rotary drum furnaces thepreheated mixture then is conveyed to an intermediate bunker of a smallsize. From there the heated mass after a short time without coming intocontact with air is delivered into the larry car which advantageously isinsulated, and then charged into the coking chamber. Where horizontalchamber ovens are used for the execution of' my coking process, themixture is charged preferably through one sole charging hole disposed inthe midst of the coking chamber, since the dry mixture is distributeduniformly on the chamber almost without any cuter help.

According to the composition of the mixture and to the temperatureobtainable in the preheating treatment the carbonization time is reducedabout to half that required for medium temperature 'car bonizationwithout preheating treatment of the mixture. In other words, for thesame output the plant can be designed half as great as and thus at lowercosts, than hitherto.

Finally, the preheating treatment aifords the ad- I vantage that abetter and more uniform medium temperature coke is obtained.

, I'wish it to be understood that the preceding specification describesonly an example of one way of carrying out my invention which,however,-is not confined to this example. On the contrary, variousmodifications may be provided in the process above described, without inany way departing from'the spirit of the invention as defined intheappended claim, and the right to make subsequent claimscther than thefollowing is expressly reserved.

What Iclaim is:

A method of making medium temperature coke by which the coking periodisreduced about one half from well coking, finely divided bituminous coaland similarly caking carbonizable fuel in a coking chamber consisting ofceramic material heated by'exterrifally applied heat which processcomprises; separately. preliminarily preheating a mixture: consisting ofabout 55% to 60% of well coking coal rich in bright coal and having ahigh content of binding'substances and low temperature coke, prior tointroducing the mixture into the coking chamber, upto a temperatureapproxim ating but lying below that point at which the mixture softensand cakes together; charging the mixture in such preheated conditioninto the coking chamber and coking the same therein separately from thepreheating by externally applying heat to thewalls of the coking'chambertov a maximum temperature of from 600 to 750 Centigrade, 'measured onthe inner side of the a chamber wall, throughout the carbonization toeffect and complete thecarbonization; and withdrawing the coke formed assoon as condensible hydrocarbons cease to escape from mixture.

'WILHlLLM FITZ.

the coking v

